This application corresponds to Japanese Patent Application No.11-337502 filed in JPO on Nov. 29, 1999, the entire disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an engine fuel-injection control device for controlling the amount of fuel that is injected at startup of an engine.
2. Description of the Related Art
Conventionally, control of fuel injection at startup of an engine, such as a diesel engine, is performed according to the fuel injection amount at startup, which is determined on the basis of the cooling water temperature, rotation speed of the engine and so forth. However, when startup problems arise, it has been proposed to add a predetermined fuel injection amount stepwise to the fuel injection amount at startup according to the amount of time that has elapsed since startup was initiated.
Control of the kind described above, of a fuel injection amount through stepwise addition to the fuel injection amount at startup, is disclosed, for example, in Japanese Patent Application Laid-Open No. S58-162738. The control of a fuel injection amount that is disclosed in this publication previous, during startup of an engine, of a startup supply amount that is added stepwise or linearly according to time or the engine speed, within a predetermined range for the engine speed. If the fuel injection amount is added to on a continuous basis, the fuel injection amount becomes excessive with respect to the amount of air intake by the engine, and there is a risk of smoke generation and an increased amount thereof, as a result of incomplete combustion of fuel. An excessive fuel-injection amount is linked to an adverse impact on fuel economy, and, since the discharge of smoke is environmentally unfavorable, the continuous addition of a fuel-injection amount is unfavorable even at startup.
Also in the fuel injection control disclosed in the above-mentioned publication, when the engine speed (or supplied fuel amount) becomes larger than a predetermined value, at least a limit value corresponding to the engine speed is provided, and a target value for the supplied fuel amount is controlled such that the fuel injection amount added does not exceed the limit value. However, the conventional constitution is such that, at engine startup, since instability of the engine rotation speed leads to abrupt fluctuations thereof, even when addition to the fuel-injection amount is regulated, the limit value itself, for this regulation, fluctuates considerably, which results in the fuel injection amount becoming unstable.
Therefore, problems to be resolved by the present invention are as follows. When the engine is starting up, an addition must not always be made to the fuel injection amount, conditions for the time when the accelerator is actuated are to be set for the addition of fuel, an increase in the amount of smoke is to be suppressed, and engine startup efficiency is to be improved.
An object of the present invention is to solve the above-mentioned problems by providing an engine fuel-injection control device that, when the engine is starting up performs control of the addition to the fuel injection amount by making accelerator actuation a condition therefore, such that, when the accelerator is not actuated, no such addition to the fuel injection amount is performed, an increase in the amount of smoke is suppressed, and engine startup efficiency is improved.
The present invention relates to an engine fuel-injection control device that comprises means for calculating a base fuel-injection amount at startup, which calculates a base fuel injection amount at startup, at startup of the engine; means for calculating an additional fuel injection amount at startup, which calculates an additional fuel injection amount at startup by adding a predetermined additional fuel injection amount to the previous target fuel-injection amount at startup; means for calculating a limit fuel-injection amount at startup, which calculates, on the basis of the accelerator actuation amount an injectable limit fuel-injection amount at startup that is limited by a boundary value at which smoke generation occurs at the above-mentioned engine startup; and means for electing a target fuel-injection amount at startup that elects the above-mentioned base fuel-injection amount at startup, which is calculated by the above-mentioned means for calculating a base fuel-injection amount at startup as the current above-mentioned target fuel-injection amount at startup if the accelerator is not actuated at the above-mentioned engine startup, or that elects the smaller of two values that are the above-mentioned additional fuel injection amount at startup and the above-mentioned limit fuel-injection amount at startup, as the current above-mentioned target fuel-injection amount at startup, if the accelerator is actuated at the above-mentioned engine startup.
By means of this engine fuel-injection control device, when the accelerator is not actuated at engine startup, the base fuel-injection amount at startup, which is calculated on the basis of the cooling water temperature and the engine rotation speed, is elected as the current target fuel-injection amount at startup; or, when the accelerator is actuated at engine startup, the smaller of two values that are the additional fuel injection amount at startup, which is calculated on the basis of the previous target fuel-injection amount at startup, and a limit fuel-injection amount at startup, is elected as the current target fuel-injection amount at startup. Consequently, addition to the fuel injection amount is only performed when the accelerator is actuated, for example by the accelerator pedal being depressed. Further, the target fuel-injection amount at startup, which is added, is elected such that the added target fuel-injection amount at startup does not exceed the limit fuel-injection amount at startup calculated on the basis of the accelerator actuation amount.
By electing the above-mentioned target fuel-injection amount at startup, consideration to whether the accelerator has been actuated having been taken as a condition for the addition of fuel, and the limit fuel-injection amount at startup having been determined in accordance with the magnitude of the accelerator actuation amount, no addition to the fuel injection amount is made if the accelerator is not actuated; furthermore, since the addition to the fuel injection amount at startup is suppressed in accordance with the magnitude of the accelerator actuation amount, the problems of smoke generation and an unfavorable impact on fuel economy can be resolved. Further, since the accelerator actuation amount does not generate abrupt fluctuations of the rotation speed of the engine at startup, the limit fuel-injection amount at startup is also stabilized.
In this engine fuel-injection control device, the above-mentioned means for calculating the limit fuel-injection amount at startup calculates the above-mentioned limit fuel-injection amount at startup in accordance with the above-mentioned engine cooling water temperature. Since it is known that, typically, the startup characteristics fluctuates considerably according to the engine cooling water temperature, it is possible to take startup efficiency and smoke suppression to a higher level while making both possible, through modification of the limit fuel-injection amount at startup in accordance with the cooling water temperature.
The above-mentioned engine fuel-injection control device preferably comprises minimum value selecting means that select the smaller of two values that are the above-mentioned additional fuel injection amount at startup, which is calculated by the above-mentioned means for calculating the additional fuel injection amount at startup; and the above-mentioned limit fuel-injection amount at startup, which is calculated by the above-mentioned means for calculating the limit fuel-injection amount at startup.
The above-mentioned means for electing a target fuel-injection amount at startup preferably elects the above-mentioned base fuel-injection amount at startup, which is calculated by the above-mentioned means for calculating a base fuel-injection amount at startup, as the current above-mentioned target, fuel-injection amount at startup, irrespective of whether the accelerator has been actuated or not, until a predetermined time has elapsed since the initiation of engine startup.
The above-mentioned means for calculating a base fuel-injection amount at startup preferably calculates the above-mentioned base fuel-injection amount at startup on the basis of the above-mentioned engine water temperature and rotation speed.
The engine fuel-injection control device relating to the present invention is preferably applied to a common-rail type diesel engine comprising: a high-pressure supply pump; a common rail for retaining fuel that is conveyed under pressure from this high-pressure supply pump; injectors for injecting the fuel supplied from the above-mentioned common rail into engine combustion chambers when an electromagnetic actuator is driven; and a controller for providing the above-mentioned electromagnetic actuator, at a predetermined time and over a predetermined duration with a control current for driving the above-mentioned electromagnetic actuator.
The above-mentioned means for calculating a base fuel-injection amount at startup, the above-mentioned means for calculating an additional fuel injection amount at startup, the above-mentioned means for calculating a limit fuel-injection amount at startup and the above-mentioned means for electing a target fuel-injection amount at startup are preferably comprised by the above-mentioned controller.
The engine fuel-injection control device relating to the present invention comprises a device for calculating a base fuel-injection amount at startup, which calculates a base fuel-injection amount at startup, at startup of the engine; a device for calculating an additional fuel injection amount at startup, which calculates an additional fuel injection amount at startup by adding a predetermined additional fuel injection amount to the previous target fuel-injection amount at startup; a device for calculating a limit fuel-injection amount at startup, which calculates, on the basis of the accelerator actuation amount, an injectable limit fuel-injection amount at startup that is a boundary value at which smoke generation occurs at the above-mentioned engine startup; and a device for electing a target fuel-injection amount at startup that elects the above-mentioned base fuel-injection amount at startup, which is calculated by the above-mentioned device for calculating a base fuel-injection amount at startup, as the current above-mentioned target fuel-injection amount at startup if the accelerator is not actuated at the above-mentioned engine startup; or that elects the smaller of two values that are the above-mentioned additional fuel injection amount at startup and the above-mentioned limit fuel-injection amount at startup, as the current above-mentioned target fuel-injection amount at startup if the accelerator is actuated at the above-mentioned engine startup.
The above-mentioned device for calculating a limit fuel-injection amount at startup is preferably constructed so as to calculate the above-mentioned limit fuel-injection amount at startup in accordance with the above-mentioned engine cooling water temperature.
The above-mentioned engine fuel-injection control device preferably comprises a minimum value selecting device that selects the smaller of two values that are the above-mentioned additional fuel injection amount at startup, which is calculated by the above-mentioned device for calculating the additional fuel injection amount at startup; and the above-mentioned limit fuel-injection amount at startup, which is calculated by the above-mentioned device for calculating the limit fuel-injection amount at startup.
The above-mentioned device for electing a target fuel-injection amount at startup preferably elects the above-mentioned base fuel-injection amount at startup, which is calculated by the above-mentioned device for calculating a base fuel-injection amount at startup, as the current above-mentioned target fuel-injection amount at startup, irrespective of whether the accelerator has been actuated or not, until a predetermined time has elapsed since the initiation of engine startup.
The above-mentioned device for calculating a base fuel-injection amount at startup preferably calculates the above-mentioned base fuel-injection amount at startup on the basis of the above-mentioned engine water temperature and rotation speed.
The engine fuel-injection control device relating to the present invention is preferably applied to a common-rail type diesel engine comprising: a high-pressure supply pump; a common rail for retaining fuel that is conveyed under pressure from this high-pressure supply pump; injectors for injecting the fuel supplied from the above-mentioned common rail into engine combustion chambers when an electromagnetic actuator is driven; and a controller for providing the above-mentioned electromagnetic actuator, at a predetermined time and over a predetermined duration, with a control current for driving the electromagnetic actuator.
The above-mentioned device for calculating a base fuel-injection amount at startup, the above-mentioned device for calculating an additional fuel injection amount at startup, the above-mentioned device for calculating a limit fuel injection amount at startup and the above-mentioned device for electing a target fuel-injection amount at startup are preferably constituted by the above-mentioned controller.
The engine fuel-injection control method relating to the present invention comprises: a step of calculating a base fuel-injection amount at startup, in which a base fuel-injection amount at startup is calculated at startup of the engine; a step of calculating an additional fuel injection amount at startup, in which an additional fuel injection amount at startup is calculated by adding a predetermined additional fuel injection amount to the previous target fuel-injection amount at startup; a step of calculating a limit fuel-injection amount at startup, in which, on the basis of the accelerator actuation amount, an injectable limit fuel-injection amount at startup is calculated that is a boundary value at which smoke generation occurs at the above-mentioned engine startup; and a step of electing a target fuel-injection amount at startup, in which the above-mentioned base fuel-injection amount at startup, which is calculated in the above-mentioned step of calculating a base fuel-injection amount at startup, is elected as the current above-mentioned target fuel-injection amount at startup if the accelerator is not actuated at the above-mentioned engine startup; or in which the smaller of two values that are the above-mentioned additional fuel injection amount at startup and the above-mentioned limit fuel-injection amount at startup, is elected as the current above-mentioned target fuel-injection amount at startup, if the accelerator is actuated at the above-mentioned engine startup.
The above-mentioned step of calculating a limit fuel-injection amount at startup is preferably constructed such that the above-mentioned limit fuel-injection amount at startup is calculated in accordance with the above-mentioned engine cooling water temperature.
The above-mentioned engine fuel-injection control method relating to the present invention preferably comprises a step of selecting a minimum value, in which the smaller of two values is selected that are the above-mentioned additional fuel binjection amount at startup, which is calculated by the above-mentioned step of calculating the additional fuel injection amount at startup, and the above-mentioned limit fuel-injection amount at startup, which is calculated in the above-mentioned step of calculating the limit fuel-injection amount at startup.
The above-mentioned step of electing a target fuel-injection amount at startup preferably elects the above-mentioned base fuel-injection amount at startup, which is calculated in the above-mentioned step of calculating a base fuel-injection amount at startup, as the current above-mentioned target fuel-injection amount at startup, irrespective of whether the accelerator has been actuated or not, until a predetermined time has elapsed since the initiation of engine startup.
The above-mentioned step of calculating a base fuel-injection amount at startup preferably calculates the above-mentioned base fuel-injection amount at startup on the basis of the above-mentioned engine water temperature and rotation speed.
The engine fuel-injection control method relating to the present invention is preferably applied to a common-rail type diesel engine comprising: a high-pressure supply pump; a common rail for retaining fuel that is conveyed under pressure from this high-pressure supply pump; injectors for injecting the fuel supplied from the above-mentioned common rail into engine combustion chambers when an electromagnetic actuator is driven; and a controller for providing the above-mentioned electromagnetic actuator, at a predetermined time and over a predetermined duration, with a control current for driving the electromagnetic actuator.
The above-mentioned step of calculating a base fuel-injection amount at startup, the above-mentioned step of calculating an additional fuel injection amount at startup, the above-mentioned step of calculating a limit fuel-injection amount at startup, and the above-mentioned step of electing a target fuel-injection amount at startup are preferably executed by the above-mentioned controller.